Many different types of lighting-control systems have been developed to help reduce energy waste, while still providing acceptable lighting levels. Dimming lighting controls may reduce lighting energy consumption and produce energy savings, while allowing a user to adjust the intensity of a light source to a desired level. Step dimming controls may allow a user to selectively operate a light source at at least two different outputs, typically at a full power output and at a less than full power output.
Two wall switches may be used in typical step dimming applications, each providing mains power through line power leads, also referred to as “hot” or “active” leads, to a light source. When both switches are in the “on” position, power is provided from the two line power leads, resulting in full light output. If one switch is in the “off” position, thus disconnecting the mains from one of the line power leads, the power is provided from the remaining connected line power lead, resulting in a dimmed light level.
U.S. Pat. No. 8,072,158, issued on Dec. 6, 2011, discloses a step dimming circuit that includes a diode bridge, an opto-isolator, and various discrete resistors and capacitors components. However, the disclosed step dimming circuit has a relatively large number of components, requiring a correspondingly large number of interconnections.
In order to utilize two switch step dimming in LED applications, a special driver that utilizes two line power lead lines may be required. Furthermore, even with a special driver, the two line power leads are typically required to have the same phase because applying different phases to the special driver at the same time may result in the applied voltage exceeding the voltage limitations of the special driver, leading to possible unreliable operation or failure. The possibility of providing different phases to the special driver may present a particular risk in retrofit applications where the exact wiring configuration may be unknown. Another solution might include using two LED drivers, each operating on a different phase. However, this would incur the cost of two LED drivers and complicated connections between the LED drivers and the LED light source.
It would be advantageous to provide step dimming for LED applications that utilizes fewer components and a standard LED driver with control leads as opposed to a special step dimming driver.